UW Study Finds That Beavers Help Keep Riparian Systems Healthy

February 21, 2014 — In some circles, beavers have long been considered pests
that damage trees, clog up culverts, and build dams that inhibit or alter the natural
flow of waterways. But, to two University of Wyoming researchers, the crafty
critters are viewed as natural allies that actually can help keep riparian
systems healthy in the short and long term.

Results of a recent study of the Pole Mountain Recreation
Area in the Medicine Bow National Forest reveal that beavers can be helpful
managers of ecological and hydrological systems.

“The goal of this project was to better understand how
beavers impact riparian systems and gain an understanding for how managers
might be able to use beavers to enact desired habitat/hydrology management
strategies,” says Matthew Hayes, a spatial analyst with the Wyoming Cooperative Fish and Wildlife
Research Unit at UW.

Hayes, a native of Hastings, Mich., was a UW graduate student
who presented his master’s thesis on the subject during November 2012. Scott
Miller, associate professor in the Department
of Ecosystem Science and Management, served as Hayes’ faculty mentor.

“Historical momentum has been that they are viewed as
pests,” Miller says of beavers. “Maybe their positive environmental benefits
are being overlooked.”

Management of riparian systems provides water for plants,
animals and people -- livestock operations and erosion control. Riparian
systems are particularly important in the Mountain West. Such systems occupy
less than 2 percent of land area while providing forage and habitat for more
than 80 percent of the region’s wildlife species, Hayes says.

Leave it to the
beavers

The study determined that, when beaver numbers increase in a
habitat and trapping of the animal stops, willow counts improve while aspen and
conifer numbers decrease. Beavers forage on aspen and use it to build dams.

As a result of the beavers’ action, trout, amphibian,
songbird and moose habitat is increased, and foraging for winter ungulate
(hooved animals such as deer, elk and moose) improves. This is because, when
beavers build dams, the local water table rises.

More water becomes available and accessible to plants which,
in turn, increases the width of the riparian system and provides more food for
animals and aquatic life. The increased water table can be crucial to these
species, especially if rainfall levels are limited in arid systems like
Wyoming.

Beaver ponds store water from snowmelt and rainfall runoff
events, and slowly release water over time as damming slows water movement. Beavers
provide optimal brook trout habitat in southeastern Wyoming and other places in
the West, and can be viewed positively by sportsmen, Miller says.

While riparian systems benefit in from the presence of
beavers, there also is a positive cycle when beavers leave an area, Hayes says.

When beaver ponds disappear due to beaver trappings or
relocation of the animals, aspen and conifer numbers increase while willow
numbers dwindle. Lowered water tables and reduced pressure from beavers are
likely reasons aspen bounced back or were converted to conifer, according to
the study. Thermal cover increases; nutrient and vegetation cycling go up; and
there is regrowth of mature, woody vegetation, with aspen being a notable
beneficiary.

The study surprisingly revealed that the vegetation composition
in areas influenced by beavers can be altered in as little as eight years.

“This relatively short length required for vegetation to
change will allow managers to alter beaver management strategies for desired
vegetation outcomes,” says Hayes, who also received his bachelor’s degree, in
wildlife fisheries biology and management, from UW. “This same technique can be
applied statewide.”

“Beavers are perceived as taking away from riparian areas,”
Miller says. “But what Matt’s study shows is that when beavers move out of an
area and the dam fails, you can have a desirable vegetative community become
established fairly quickly.”

Hayes and Miller say they do not have an accurate count of
how many beavers currently inhabit the Pole Mountain area. A 1974 survey, the
last time a beaver count was taken there, estimated 272 beavers lived in the
area.

Going high tech

Hayes and Miller examined riparian vegetation composition
within 100 meters of beaver ponds that were gained or lost between 2001 and
2009, as well as areas, between 1994 and 2009, that were never ponded. This
provided the research team two snapshots in time of the area’s land cover.
These two periods -- using photos from the very high-resolution National
Agriculture Imagery Program (NAIP) -- were compared to determine changes to
vegetation over time.

That process could have been
laborious and incredibly time intensive, as Hayes' analysis covered a
56,000-acre study area and focused on nine primary stream channels within the
recreation area.

But Hayes developed a
remote sensing system -- using a laser range finder that communicates
wirelessly with a hand-held GPS system. The laser range finder obtained the
training data needed to map vegetation at a 1-meter spatial scale. Using Random
Forests (a machine-learning algorithm), with the aid of NAIP and ancillary data,
Hayes developed a model that was able to map vegetation at a 1-meter spatial
scale.

“This is important because most of the data that we have for
land cover is 30-meter spatial scale. A large contribution of our work was
developing the methods to accurately map vegetation at a 1-meter spatial
resolution,” Hayes says. “NAIP data is generally poor for remote sensing
application such as this but, using Random Forests, we were able to create a
technique to model vegetation.”

To do this, a data management system was set up within the
GPS device to collect field data. The system was created so that every
collected point was associated with a certain type of vegetation the team
researched. These included conifer, aspen, willow, grass, beaver ponds, rock
outcrop and uplands.

Total time spent in the field to compile this data was less
than eight days, Hayes says.

“These are important tools, but fairly new to the management
community,” Hayes says. “One of the major reasons to do this work is to
minimize field work and get accurate answers you need for future mapping
efforts.”

Hayes has made his models available to the Wyoming Game and
Fish Department Aquatic Habitat Division, which funded the research. The
organization is interested in the feasibility of using beavers to enhance
ecological services and assist managers in watershed restoration efforts.

The research described in his master’s thesis can be used as
a baseline for further studies in this area to assist in understanding riparian
nutrient cycling and alterations to hydrologic regimes, Hayes says. He adds
that Colorado, Idaho and western portions of Montana -- states with riparian
habitat at elevation -- also may benefit from his work.

Miller views the interdisciplinary research as unique, as it
combined ecology, hydrology and high technology.

“This research merged my interests in wildlife and
management tools to find different ways to manage wildlife problems,” Hayes
says.

The research Hayes conducted to develop his remote imaging
system was published in Remote Sensing Letters earlier this year. He currently
is prepping his beaver findings with plans to submit a paper to the Journal of
Wildlife Management for possible publication.

Photo:Matt Hayes, a spatial analyst with the Wyoming
Cooperative Fish and Wildlife Research Unit, wrote his master’s thesis on his
research that shows beavers can be used as managers to ensure healthy riparian
systems. (Stock Photo)